Organic el light emitting element, manufacturing method thereof, and display device

ABSTRACT

An organic EL light emitting element is provided with a conductive transparent electrode  3,  a counter electrode  8  opposing the conductive transparent electrode  3,  an organic EL light emitting layer  6  provided between the conductive transparent electrode  3  and the counter electrode  8,  an insulating protection layer  9  provided to cover at least the organic EL light emitting layer  6,  and a heat dissipating layer  11  which is brought into contact with the insulating protection layer  9.  The conductive transparent electrode has an ITO film including at least one of Hf, V and Zr at least on the surface part on the side of the organic EL light emitting layer  6,  and the insulating protection layer 9 includes a nitride film having a thickness of 100 nm or less.

TECHNICAL FIELD

This invention relates to a light emitting element, such as a displayelement, particularly an organic electro-luminescence (EL) displayelement and, in particular, relates to an improvement in a protectivelayer of such a light emitting element.

BACKGROUND ART

In recent years, self-luminous organic electro-luminescence (EL) displaydevices have been actively studied as display devices that can achievehigh brightness while being of the thin type. An organic EL element hasa structure in which an organic layer serving as a light emitting layeris sandwiched between opposing electrodes, and the light emission iscontrolled by on/off of the current to the electrodes, thereby forming adisplay device. The display devices are classified into a passive matrixtype and an active matrix type. The former is used as a backlight or arelatively low definition display device and the latter is used as arelatively high definition display device such as a television or amonitor.

In organic EL elements forming such organic EL display devices, a largeproblem is that an organic layer has a short lifetime which serves as alight emitting layer. Although the light emission time has beenincreasing through various studies in recent years, the current elementlifetime is still short when used, for example, for a television or amonitor, and the brightness is reduced by half in 2000 to 3000 hours inthe case of continuous lighting. As a reason for the short elementlifetime, invasion of moisture into the organic layer serving as thelight emitting layer or thermal destruction due to heating afterformation of the organic layer or due to heat generation of the elementis notable, and various improvements have been improved.

Organic EL light emitting elements of this type are described inJapanese Unexamined Patent Application Publication (JP-A) No. H10-275680and Japanese Unexamined Patent Application Publication (JP-A) No.2002-343559 (hereinafter referred to as Patent Document 1 and PatentDocument 2). Among them, Patent Document 1 discloses the organic ELlight emitt8ing elements having a protective film in the form of amultilayer structure including two layers, i.e. an organic layer and ametal layer, or two layers, i.e. an inorganic layer and a metal layer.

On the other hand, Patent Document 2 discloses an organic EL lightemitting latyer in which a heat dissipating plate of metal is providedas a heat dissipating member on one of electrodes forming an organic ELelement, through an adhesive layer.

In Patent Document 1, when the two layers including the organic layerand the metal layer are employed as the protective film, a problemarises that the thermal conductivity of the organic layer is low andthus the heat generated in the element cannot be sufficiently dissipatedor radiated. On the other hand, in the case of the two layers includingthe inorganic layer and the metal layer, when use is made of SiO₂ citedin the Document as an example of a semiconductor compound forming theinorganic protective film, a problem is that the thermal conductivity ofSiO₂ is low and thus the heat generated in the element cannot besufficiently dissipated or radiated and, further, it is not possible tosufficiently prevent invasion of moisture as the protective film.

According to Patent Document 2, the problem of heat dissipation can beavoided, but a problem has arisen that a space is formed at a separationportion between light emitting elements in the form of a passive matrixstructure and an organic solvent or moisture generated from an adhesiveremains at this portion or the adhesive enters this portion, and thusthe light emitting layer protection, which is most important, cannot besecurely achieved, thereby reducing the element lifetime.

Further, a problem has arisen that since a method of forming theforegoing protective film is generally performed at a temperature thatdoes not decompose an organic layer, it is not possible to form a finethin film and, therefore, it is necessary to form a protective filmhaving a thickness of several hundred nanometers to several microns inorder to prevent permeation of moisture or organic compounds, resultingin an increase in thermal resistance to raise the temperature of anelement to thereby shorten the lifetime thereof. As described above,although it is essential to prevent the incorporation of moisture ororganic compounds into a light emitting layer and electronic layers andefficiently remove the heat generated in an element for increasing thelifetime of an organic EL element and an organic EL display device,effective means have not yet been proposed.

DISCLOSURE OF THE INVENTION

This invention has been made in consideration of the foregoing problemsand provides a long-lifetime organic EL element and a long-lifetimeorganic EL display device, and a method and apparatus for manufacturingthem, which, specifically, will be described hereinbelow.

That is, according to one aspect of the present invention, there isprovided an organic EL light emitting element, which includes aconductive transparent electrode, a counter electrode opposed to theconductive transparent electrode, an organic EL light emitting layerprovided between the conductive transparent electrode and the counterelectrode, an insulating protective layer provided to cover at least theorganic EL light emitting layer, and a heat dissipating layer providedto be in contact with the insulating protective layer. In the aspect ofthe present invention, at least a surface portion of the conductivetransparent electrode on the side of the organic EL light emitting layerincludes an ITO film containing at least one of Hf, V and Zr. Theinsulating protective layer includes a nitride film having a thicknessof 100 nm or less.

In the aspect of the present invention, it is preferred that the nitridefilm is composed of at least one of compounds of nitrogen and an elementselected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, B, Aland Si, and more preferred that the nitride film is composed of at leastone of silicon nitride, titanium nitride, tantalum nitride and aluminumnitride.

Since a nitride film is finer than an oxide film, it is excellent inmoisture prevention effect and heat dissipation effect as compared withthe oxide film.

Since the heat dissipation efficiency increases as the thicknessdecreases, it is necessary to minimize the thickness as long as thefunction as a protective film is ensured and, from this aspect, it isset to 100 nm or less, preferably 30 nm to 50 nm. The insulatingprotective layer may comprise an insulating layer covering the organicEL light emitting layer through the counter electrode and a protectivelayer covering the insulating layer. This structure is necessaryparticularly when the protective layer is conductive.

This invention is also applicable to general display elements other thanthe organic EL element,

The present invention can be applied to a general display element otherthan the organic EL light emitting element.

According to another aspect of the present invention, there is provideda display element which includes a conductive transparent electrode, acounter lectrode opposed to the conductive transparent electrode, alight emitting layer provided between the conductive transparentelectrode and the counter electrode, a protective layer covering atleast the light emitting layer, and a heat dissipating layer contactingthe protective layer. In the display elemen, it is preferred that atleast a surface portion of the conductive transparent electrode includesan ITO film containing at least one of Hf, V and Zr.

In the other aspect of the present invention, the protective layer maycontain at least an element selected from the group consisting of Ar,Kr, and Xe.

According still another aspect of the present invention, there isprovided a method of manufacturing a light emitting element. The lightemitting element includes a conductive transparent electrode, a counterelectrode opposed to the conductive transparent electrode, a lightemitting layer provided between the conductive transparent electrode andthe counter electrode, and a protective layer provided to cover at leastthe light emitting layer. In the aspect of the present invention, themethod includes the step of forming the protective layer using a plasmacontaining, as a main component, a gas selected from the groupconsisting of Ar, Kr and Xe.

In the aspect of the present invention, it is preferred that the plasmais a plasma excited by a high frequency. Particularly, the highfrequency is a microwave.

In the aspect of the present invention, it is also preferred that theprotective layer is formed by low-temperature vapor deposition that isperformed at 100° C. or less and, preferably, at room temperature. It ismore preferred that The low-temperature vapor deposition is performedwithout heating excepting in a case of the plazuma heating.

According to yet another aspect of the present invention there isprovided an organic EL display device.

The organic EL display device includes a plurality of gate lines and aplurality of signal lines arranged in a matrix, switching elementsprovided at intersections of the gate lines and the signal lines,conductive transparent electrodes, counter electrodes opposed to theconductive transparent electrodes, organic EL light emitting layersprovided between the conductive transparent electrodes and the counterelectrodes, respectively, a protective layer provided to cover at leastthe organic EL light emitting layers, and a heat dissipating layerprovided to be in contact with the protective laye. In the organic ELdisplay device, the switching elements are TFTs, each of the TFTs havinga gate electrode connected to the gate line, a signal line electrodeconnected to the signal line, and a pixel electrode connected to theconductive transparent electrode or the counter electrode through acontact hole formed in an insulating film covering the TFTs, at least asurface portion of each of the conductive transparent electrodes on theside of the organic EL light emitting layer including an ITO filmcontaining at least one of Hf, V and Zr.

On the other hand, another organic EL display device includes aplurality of gate lines and a plurality of signal lines arranged in amatrix on a substrate, switching elements provided at intersections ofthe gate lines and the signal lines, conductive transparent electrodes,counter electrodes opposed to the conductive transparent electrodes,organic EL light emitting layers provided between the conductivetransparent electrodes and the counter electrodes, respectively, aprotective layer provided to cover at least the organic EL lightemitting layers, and a heat dissipating layer provided to be in contactwith the protective layer. In the other organic EL display device, theswitching elements are TFTs each of which having a gate electrodeconnected to the gate line, a signal line electrode connected to thesignal line, and a pixel electrode connected to the conductivetransparent electrode or the counter electrode, the gate lines and thegate electrodes being embedded in the substrate or in an insulating filmformed to be in contact with the substrate.

In the aspect of the present invention, it is preferred that at least asurface portion of each of the conductive transparent electrodes on theside of the organic EL light emitting layer includes an ITO filmcontaining at least one of Hf, V and Zr and the protective layerincludes a nitride film having a thickness of 100 nm or less.

According to a further aspect of the present, there is provided a methodof manufacturing a conductive transparent film which includes the stepof performing sputtering film formation using a plasma containing Kr orXe as a main component.

According to a still further aspect of the present invention, there isprovided a method of manufacturing a conductive transparent film whichincludes the steps of forming an ITO film by sputtering of a targetcontaining indium oxide and tin oxide using a plasma excited by a highfrequency, and performing the sputtering using the plasma containing atleast one of Kr and Xe as a main component.

According to a still further aspect of the present invention, there isprovided a method of forming a nitride film which includes the step ofperforming vapor deposition of a nitride film using a microwave-excitedplasma, wherein the step of the vapor deposition is performed using theplasma containing at least one of Ar, Kr and Xe as a main component andat a low temperature without-heating except heating by the plasma.

In the method, it is preferred that the microwave-excited plasma vapordeposition is performed by the steps of using a plasma processingapparatus having dual shower plates, introducing a gas containing atleast one of Ar, Kr and Xe into the apparatus from the upper showerplate to generate the plasma, and introducing a material gas of thenitride film into the plasma from the lower shower plate.

It is also preferred that at the time of the vapor deposition of thenitride film, a high frequency is applied to a film-forming member tothereby generate a bias potential on a surface of the film-formingmember.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a sectional view showing the structure of a bottom emissiontype passive display element of Embodiment 1 of this invention;

FIG. 1B is a plan view showing the structure of the bottom emission typepassive display element of FIG. 1A;

FIG. 2 is a diagram showing a schematic structure of a dual shower platemicrowave-excited high-density plasma film forming apparatus used in theEmbodiment;

FIG. 3A is a sectional view showing the structure of a top emission typepassive display element of Embodiment 2 of this invention;

FIG. 3B is a plan view showing the structure of the top emission typepassive display element of FIG. 3A;

FIG. 4A is a sectional view showing part of pixels of a bottom emissiontype passive matrix organic EL display device of Embodiment 3 of thisinvention;

FIG. 4B is a plan view showing part of the pixels of the bottom emissiontype passive matrix organic EL display device of FIG. 4A;

FIG. 5A is a sectional view showing part of pixels of a top emissiontype passive matrix organic EL display device of Embodiment 4 of thisinvention;

FIG. 5B is a plan view showing part of the pixels of the top emissiontype passive matrix organic EL display device of FIG. 5A;

FIG. 6A is a sectional view showing part of pixels of a bottom emissiontype active matrix organic EL display device of Embodiment 5 of thisinvention;

FIG. 6B is a plan view showing part of the pixels of the bottom emissiontype active matrix organic EL display device of FIG. 6A;

FIG. 7A is a sectional view showing part of organic EL elementsaccording to Embodiment 6 of this invention;

FIG. 7B is a plan view showing part of the organic EL elements of FIG.

7A;

FIG. 8A is a sectional view showing part of pixels of a top emissiontype active matrix organic EL display device of Embodiment 7 of thisinvention;

FIG. 8B is a plan view showing part of the pixels of the top emissiontype active matrix organic EL display device of FIG. 8A;

FIG. 9A is a sectional view showing part of an organic EL display deviceaccording to Embodiment 8 of this invention;

FIG. 9B is a plan view showing part of the organic EL display device ofFIG. 9A;

FIG. 10A is a sectional view showing part of an organic EL displaydevice according to Embodiment 9 of this invention;

FIG. 10B is a plan view showing part of the organic EL display device ofFIG. 10A;

FIG. 11A is a sectional view showing part of an organic EL displaydevice according to Embodiment 10 of this invention;

FIG. 11B is a plan view showing part of the organic EL display device ofFIG. 11A;

FIG. 12A is a sectional view showing part of an organic EL displaydevice according to Embodiment 11 of this invention;

FIG. 12B is a plan view showing part of the organic EL display device ofFIG. 12A;

FIG. 13A is a sectional view showing part of an organic EL displaydevice according to Embodiment 12 of this invention;

FIG. 13B is a plan view showing part of the organic EL display device ofFIG. 13A;

FIG. 14A is a sectional view showing part of an organic EL displaydevice according to Embodiment 13 of this invention;

FIG. 14B is a plan view showing part of the organic EL display device ofFIG. 14A; and

FIG. 15 is a sectional view showing one example of a heat dissipatinglayer according to Embodiment 14 of this invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, Embodiments of this invention will be described withreference to the drawings.

Embodiment 1

Referring to FIGS. 1A and 1B, a bottom emission type passive displayelement 1 according to Embodiment 1 includes a transparent substrate 2,a conductive transparent electrode 3 formed on the transparent substrate2, a hole transport layer 5, a light emitting layer 6, and an electrontransport layer 7 which form an organic layer 10 stacked on theconductive transparent electrode 3, a counter electrode 8 stacked on theorganic layer 10, a protective layer 9 formed to cover them, and a heatdissipating layer 11 formed to be in contact with the protective layer9.

As the transparent substrate 2, use can be made of a material adapted totransmit light radiated from the light emitting layer 6 and a glasssubstrate was used in Embodiment 1.

An indium-tin oxide (ITO) film doped with Hf ,which may be replaced by Vor Zr, was used as the conductive transparent electrode 3 for increasinga work function of its surface contacting the organic layer 10 toimprove the efficiency of hole injection into the element. This makesunnecessary a hole injection layer or a buffer layer that is generallyrequired.

The organic layer 10 is composed of the hole transport layer 5, thelight emitting layer 6, and the electron transport layer 7 and is notparticularly limited and, even if any of known materials are used, theoperation/effect of this invention is obtained. The hole transport layer5 serves to efficiently move holes to the light emitting layer 6 and tosuppress movement of electrons from the counter electrode 8 to the sideof the conductive transparent electrode 3 through the light emittinglayer 6, thereby enhancing the efficiency of recombination of electronsand holes in the light emitting layer 6.

Although not particularly limited, use can be made, as a materialconstituting the hole transport layer 5, of, for example,1,1-bis(4-di-p-aminophenyl)cyclohexane, carbazole or its derivative,triphenylamine or its derivative, or the like.

Although not particularly limited, use can be made, as the lightemitting layer 6, of quinolinol aluminum complex containing a dopant,DPVi biphenyl, or the like. Depending on use, red, green, and bluephosphors may be used by stacking them and, in a display device or thelike, red, green, and blue phosphors may be used by arranging them in amatrix.

A silole derivative, a cyclopentadiene derivative, or the like can beused as the electron transport layer 7.

No particular limitation can be made of a material forming the counterelectrode 8 and use can be made of aluminum having a work function of3.7 eV, or the like.

A nitride of an element selected from the group consisting of Ti, Zr,Hf, V, Nb, Ta, Cr, B, Al, and Si is preferable as the protective layer 9serving to prevent invasion of moisture, an oxidizing gas, or the likeinto the organic EL light emitting layer. Although a thinner thicknessis preferable in terms of reducing the thermal resistance, about 10 nmto 100 nm is preferable for preventing permeation of moisture, anoxidizing gas, or the like and 30 nm to 50 nm is more preferable.

In the case where the protective layer 9 is composed of the foregoingnitride, since the thermal conductivity is high and the thermalresistance can be reduced, the protective layer 9 can also serve as theheat dissipating layer 11. However, the heat dissipating layer 11 mayalso be provided for carrying out the heat dissipation more efficiently.

Aluminum, copper, or the like having a high thermal conductivity ispreferable as the heat dissipating layer 11.

Next, description will be made as regards a method of manufacturing thedisplay element according to this embodiment. An ITO containing 5 wt %Hf was formed into a film on the cleaned glass substrate by a sputteringmethod. The film formation employed a co-sputtering method using an ITOtarget (preferably a sintered body of indium oxide and tin oxide) and aHf target. In the sputtering, Xe having a large collision sectional areawas used as a plasma excitation gas, thereby generating a plasma havinga sufficiently low electron temperature. The substrate temperature wasset to 100° C. and the film thickness was set to 200 angstroms. AHf-doped portion was limited to a surface layer and only the undoped ITOwas used thereafter. Since the sputtering was carried out using the Xeplasma, the electron temperature was sufficiently low and, thus, even ifthe film formation was performed while irradiating Xe ions onto the ITOsurface during the film formation for improving the film quality, plasmadamage to the ITO film was suppressed and therefore the high-qualityfilm formation was achieved even at a low temperature of 100° C. orless. The Hf-containing ITO film thus formed was patterned into apredetermined shape. The patterning was performed by a photolithographymethod. A novolak-based resist was used as a photoresist and, aftercarrying out exposure using a mask aligner and development using apredetermined developer, surface organic compound removal cleaning byultraviolet irradiation was performed for 10 minutes. Then, using anorganic film vapor deposition apparatus, the hole transport layer 5, thelight emitting layer 6, and the electron transport layer 7 werecontinuously formed. Then, without exposing the substrate to theatmosphere, aluminum was deposited to form the counter electrode 8 usingan aluminum vapor deposition apparatus adjacent to the organic filmvapor deposition apparatus. Then, without exposing the substrate to theatmosphere, it was conveyed to an insulating protective film formingapparatus, where a silicon nitride film was deposited to form theinsulating protective film 9. In the silicon nitride film formation, aplasma CVD method using a microwave-excited plasma was employed, whereinuse was made of a gas with a volume ratio ofAr:N₂:H₂:SiH₄=80:18:1.5:0.5. The process pressure is preferably 0.1 to 1Torr and, in this Embodiment, it was set to 0.5 Torr. A high frequencyof 13.56 MHz was applied from the back of the substrate to therebygenerate a potential of about −5V as a bias potential on the substratesurface, and ions in the plasma were irradiated onto it. The substratetemperature was set to room temperature during the silicon nitride filmformation and heating by heating means was not performed other thanunavoidable heating by the plasma. The film thickness was set to 50 nm.

Referring to FIG. 2, a dual shower plate microwave-excited high-densityplasma film forming apparatus 12 used in the film formation has achamber in which an ion irradiation bias high-frequency power source 13is disposed and a processing object substrate 14 is placed thereover. Alower shower plate 22, an upper shower plate 23, and thereover, adielectric window 19 and a microwave radiating antenna 20 are disposedso as to be opposed to the substrate in the order named. When amicrowave is introduced as indicated by an arrow 21, gases such as Ar,H₂, and N₂ from the upper shower plate 23 become a plasma-excited gas 18in a plasma excitation region 17, while, material gases such as SiH₄ andAr are supplied from the lower shower plate 22 and reach the substratethrough a process region (plasma diffusion region) 15. This dual showerplate microwave-excited high-density plasma film forming apparatus 12uses the microwave-excited plasma and can arrange the process region ata position away from the plasma excitation region. Therefore, theelectron temperature in the process region is 1.0 eV or less even whenAr is used, and the plasma density is 10¹¹/cm² or more. Because of thedual shower plate structure having the upper shower plate 23 and thelower shower plate 22, the material gases such as the silane can beintroduced into the process region away from the plasma excitationregion and, therefore, excessive dissociation of the silane can beprevented and, even at room temperature, the light emitting element andthe formed protective film were free from a defect and it was possibleto form the fine film. By applying the high frequency from the back ofthe substrate to generate the bias potential on the substrate surfaceand irradiating ions onto the substrate surface from themicrowave-excited plasma, it was possible to finely form the nitridefilm, thereby further improving the film quality. Although the substrateis heated by the plasma as described above, it is also important not toperform heating other than that. The vapor deposition may be carried outwhile cooling the substrate for suppressing the heating by the plasma.

Thereafter, aluminum was further formed into a film with a thickness of1 micron using the aluminum vapor deposition apparatus, therebyobtaining the heat dissipating layer.

Instead of the aluminum vapor deposition, aluminum sputtering filmformation may be carried out. In this event, the sputtering filmformation using a Xe plasma with a low electron temperature iseffective.

Through the foregoing processes, the light emitting element of thisEmbodiment 1 was obtained. As a result of measuring the element lifetimeof the light emitting element of this Embodiment, the luminancehalf-decay lifetime being conventionally 2000 hours increased to 6000hours and thus the effect of the protective layer 9 was confirmed.

Embodiment 2

Referring to FIGS. 3A and 3B, a top emission type passive displayelement 24 according to Embodiment 2 includes a substrate 2, a counterelectrode 8 formed on the substrate 2 so as to be opposed to aconductive transparent electrode 3, an electron transport layer 7, alight emitting layer 6, and a hole transport layer 5 which form anorganic layer 10 stacked on the counter electrode 8, the conductivetransparent electrode 3 stacked on the organic layer 10, a transparentprotective layer 25 formed to cover them, and a transparent heatdissipating layer 26 formed to be in contact with the transparentprotective layer 25. Because of being the top emission type, although amaterial of the substrate is not particularly limited, a metal, siliconnitride, aluminum nitride, boron nitride, or the like is preferable interms of heat dissipation. In the case of using the metal substrate, thesubstrate 2 may also serve as the counter electrode 8.

The electron transport layer 7, the light emitting layer 6, and the holetransport layer 5 were stacked by the same method as that described inEmbodiment 1. Although known materials can be used as materials of therespective layers, the materials shown in Embodiment 1 are cited asexamples.

Depending on use, red, green, and blue phosphors may be used in a singlelayer or stacked layers as the light emitting layer 6.

Then, by the method shown in Embodiment 1, an ITO film containing 5 wt %Hf was formed to thereby obtain the counter electrode 8. Since the ITOfilm was formed by sputtering using a Xe plasma with a low electrontemperature, damage to the underlying organic layer 10 or the formed ITOfilm due to the plasma was not observed and it was possible to carry outhigh-quality film formation at a low temperature. Silicon nitride wasformed into a film by the method shown in Embodiment 1 so as to coverthe top emission type organic EL element thus obtained, therebyobtaining the insulating transparent protective film 25 also serving asthe heat dissipating layer 26. The thickness of this insulatingprotective film 25 was set to 50 nm. Since silicon nitride has a highthermal conductivity of 80W/(m·K) and, further, it was possible to formthe fine thin film by the microwave-excited plasma, the thermalresistance can be sufficiently reduced to thereby suppress temperaturerise of the element and, therefore, the protective layer 25 sufficientlyfunctions also as the heat dissipating layer 26. If a metal is used asthe substrate 2 and silicon nitride is used as the insulating protectivelayer 25, sufficient heat dissipation is achieved, while, the heatdissipating layer 26 may also be used separately for efficientlycarrying out the heat dissipation. No particular limitation is made of amaterial of the transparent heat dissipating layer 26 used in the topemission type as long as it has a high thermal conductivity and istransparent, and an ITO or the like is cited as an example. Theluminance half-decay lifetime of the organic EL element thus completedwas measured to be 9000 hours while being conventionally 3000 hours and,therefore, the effect of the protective layer 25 was confirmed.

Embodiment 3

Referring to FIGS. 4A and 4B, a bottom emission type passive matrixorganic EL display device 27 according to Embodiment 3 includes atransparent substrate 2, conductive transparent electrodes 3, a holetransport layer 5, a light emitting layer 6, and an electron transportlayer 7 which form each of organic layers 10 stacked on the conductivetransparent electrodes 3, respectively, counter electrodes 8 formed onthe organic layers 10, respectively, a protective layer 9 formed todirectly or indirectly cover the light emitting layers 6, and a heatdissipating layer 11. Since it is configured such that the bottomemission type organic EL display elements shown in Embodiment 1 arearranged in a matrix, those elements respectively selected by theconductive transparent electrodes 3 and the counter electrodes 8 areadapted to emit light. The conductive transparent electrodes 3 and thecounter electrodes 8 are patterned into a matrix, thereby arranging theelements. Symbol 28 denotes a light emitting portion.

As a protective film forming the protective layer 9, silicon nitride,aluminum nitride, boron nitride, or the like is preferable in terms ofinsulation between the different counter electrodes and, in Embodiment3, use was made of silicon nitride formed by the method described inEmbodiment 1. Since the elements shown in Embodiment 1 are arranged in amatrix, although the display device is simply configured, the similareffect to Embodiment 1 is obtained and thus the luminance half-decaylifetime of the elements is improved by the fine and thin protectivelayer 9. As a result of measurement, the luminance half-decay lifetimebeing conventionally 2000 hours increased to 6000 hours.

Embodiment 4

Referring to FIGS. 5A and 5B, a top emission type passive matrix organicEL display device 30 according to Embodiment 4 includes a transparentsubstrate 29, counter electrodes 8 opposed to conductive transparentelectrodes 3, an electron transport layer 7, a light emitting layer 6,and a hole transport layer 5 which form each of organic layers 10stacked on the counter electrodes 8, respectively, the conductivetransparent electrodes 3 formed on the organic layers 10, respectively,a protective layer 9 formed to directly or indirectly cover the lightemitting layers 6, and a heat dissipating layer 11. Since it isconfigured such that the top emission type organic EL display elementsshown in Embodiment 2 are arranged in a matrix, those elementsrespectively selected by the conductive transparent electrodes 3 and thecounter electrodes 8 are adapted to emit light. Since the elementscaused to emit light are selected by the counter electrodes 8 disposedon the substrate 29 and the conductive transparent electrodes 3, thesubstrate 29 is insulative and is preferably a glass or quartzsubstrate, a silicon nitride substrate, an aluminum nitride substrate, aboron nitride substrate, or the like and more preferably, in terms ofheat dissipation, the silicon nitride substrate, the aluminum nitridesubstrate, the boron nitride substrate, or the like having a highthermal conductivity. In Embodiment 4, use was made of silicon nitrideformed by the method described in Embodiment 1. Symbol 31 denotes alight emitting portion.

The conductive transparent electrodes 3 and the counter electrodes 8 arepatterned into a matrix, thereby arranging the elements. The same effectas in Embodiment 2 is obtained and thus the luminance half-decaylifetime of the elements is improved by the fine and thin protectivelayer 9. As a result of measurement, the luminance half-decay lifetimebeing conventionally 3000 hours increased to 9000 hours.

Embodiment 5

Referring to FIGS. 6A and 6B, a bottom emission type active matrixorganic EL display device 32 according to Embodiment 5 includes atransparent substrate 2, a plurality of gate lines, a plurality ofsignal lines intersecting the gate lines, switching elements disposed atintersections of the gate lines and the signal lines, conductivetransparent pixel electrodes 36 connected to the switching elements, ahole transport layer 5, a light emitting layer 6, and an electrontransport layer 7 which form each of organic layers 10 stacked on thetransparent pixel electrodes 36, respectively, counter electrodes 8formed on the organic films of the organic layers 10 so as to be opposedto the conductive transparent pixel electrodes 36, respectively, aprotective layer 9 formed to directly or indirectly cover at least theorganic layers 10, and a heat dissipating layer 11 formed to be incontact with the protective layer 9. In the organic layer 10, the holetransport layer 5, the light emitting layer 6, and the electrontransport layer 7 are formed from the side near the transparent pixelelectrode 36.

The switching element is preferably a thin-film transistor (TFT)element, a metal injection molding (MIM) element, or the like that cancontrol ON/OFF of the current. The TFT element is preferable in terms ofcontrollability of the brightness of the organic EL element.

Although it differs depending on a specification of a display device, aknown amorphous TFT or polysilicon TFT can be suitably used as the TFTelement.

Next, description will be made as regards a method of manufacturing theactive matrix organic EL display device according to Embodiment 5. Atfirst, Al was formed into a 300 nm film by sputtering on a cleaned glasssubstrate. In the sputtering, an Ar, Kr, or Xe gas can be suitably used.When Xe is used, since the electron collision sectional area is largeand the electron temperature is low, damage by a plasma to the formed Alfilm is suppressed, which is thus more preferable. Then, the formed Alfilm was patterned into gate lines and gate electrodes by aphotolithography method. Then, using the dual shower plate microwaveplasma film forming apparatus used in Embodiment 1, silicon nitride wasformed into a 300 nm film at a substrate temperature of 200° C. and atAr:N₂:H₂:SiH₄=80:18:1.5:0.5, thereby obtaining a gate insulating film33. By setting the substrate temperature to 200° C., it was possible toform a high-quality silicon nitride film having a high withstand voltageand a small interface state density and thus capable of being used asthe gate insulating film 33. Then, using the same apparatus, amorphoussilicon was formed into a 50 nm film at a substrate temperature of 200°C. and at a volume ratio of Ar:SiH₄=95:5 and, subsequently, n+ amorphoussilicon was formed into a 30 nm film at Ar:SiH₄:PH₃=94:5:1. Bypatterning the stacked amorphous silicon and n+ silicon films by aphotolithography method, element regions were formed. Then, using thesame method as that shown in Embodiment 1, an ITO containing 5 wt % Hfwas formed into a 350 nm film and then was patterned by aphotolithography method, thereby obtaining signal lines 36, signal lineelectrodes 37, and conductive transparent pixel electrodes 36. Then,using the patterned ITO film as a mask, the n+ amorphous silicon layerwas etched by a known ion etching method, thereby forming TFT channelseparating regions. Using the dual shower plate microwave plasma filmforming apparatus used in Embodiment 1, a silicon nitride film wasformed at room temperature, and then was subjected to patterning oforganic EL element regions by a photolithography method, therebyobtaining a protective film 9 at each of the TFT channel separatingportions and an insulating layer adapted to prevent a short between theconductive transparent electrode 36 and a counter electrode 8 of eachorganic EL element.

Then, using the method described in Embodiment 1, hole transport, lightemitting, and electron transport layers 5, 6, and 7 were continuouslyformed as organic layers 10 and, without exposure to the atmosphere, Alwas formed into a film using a Xe plasma with a low electron temperatureby the use of an Al sputtering apparatus used for the formation of thegate lines, thereby obtaining the counter electrodes. Then, siliconnitride was formed into a 50 nm film at room temperature by the dualshower plate microwave plasma film forming apparatus used in Embodiment1, thereby obtaining a protective layer 9. Since the protective layer 9has a high thermal conductivity of 80 W/(m·K) and is sufficiently thin,the thermal resistance is small and, therefore, it can also fully serveas a heat dissipating layer alone. However, a heat dissipating layer mayalso be provided separately for carrying out heat dissipation moreefficiently. In this Embodiment, Al was formed into a film using a Xeplasma with a low electron temperature by the use of the Al sputteringapparatus used for the formation of the gate lines, thereby obtaining aheat dissipating layer 11.

According to the bottom emission type active matrix organic EL displaydevice thus obtained, since a buffer layer or a hole injection layerbecomes unnecessary because of a high work function possessed by theHf-containing ITO film, highly efficient light emission is enabled.Further, since use is made of the protective layer 9 having a highthermal conductivity and being thin, the protective layer 9 can suppresstemperature rise of the elements while fully achieving its function as aprotective layer, so that the element lifetime can be significantlyimproved. As a result of measuring the luminance half-decay lifetime ofthe display device shown in this Embodiment, it was improved to 6000hours while being conventionally 2000 hours.

Embodiment 6

Referring to FIGS. 7A and 7B, a transparent flattening film 41 may beformed on TFTs and, thereafter, organic EL elements may be formed. Withthis configuration, the organic EL elements can be formed on a flatsurface and, therefore, the manufacturing yield is improved. Further,since an organic EL layer is formed at a layer different from a signalline layer, conductive transparent pixel electrodes 36 can be arrangedso as to extend over the signal wiring and thus it is possible toincrease an area of each light emitting element. Further, since signallines can be formed of a material different from that of the pixelelectrodes, it is not necessary to use a conductive transparent materialand, therefore, it is possible to reduce a wiring resistance when adisplay device is increased in size, thereby enabling an increase indisplay gradation. A bottom emission type active matrix organic ELdisplay device of Embodiment 6 is formed in the following manner. Atfirst, gate lines, TFT elements, and signal lines were formed by themethod described in Embodiment 5. The signal lines were obtained byforming Al into a 300 nm film by the sputtering method using a Xe gas asshown in Embodiment 6 and patterning it by a photolithography method.Then, a photosensitive transparent resin was coated by a spin coatingmethod, then was subjected to exposure and development, and then wasdried at 150° C. for 30 minutes, thereby obtaining a flattening film. Bythe foregoing exposure and development processes, the flattening filmwas formed with connecting holes each for connection between apixel-side electrode of the TFT and an organic EL element. As thephotosensitive transparent resin, there is an acrylic resin, apolyolefin resin, an alicyclic olefin resin, or the like. The alicyclicolefin resin is excellent in transparency with less moisture content andrelease and thus is preferable and, in this Embodiment, the alicyclicolefin resin was used. Then, using the method described in Embodiment 1,an ITO film containing 5 wt % Hf was formed and then was patterned by aphotolithography method, thereby obtaining conductive transparent pixelelectrodes 36. Subsequently, hole transport, light emitting, andelectron transport layers 5, 6, and 7 were continuously formed by themethod shown in Embodiment 1, and then Al was formed into a film by thesputtering method using a Xe plasma, which is likewise shown inEmbodiment 1, thereby obtaining counter electrodes. In the lightemitting layer, materials adapted to emit light in red, green, and blue,respectively, may be used by optionally stacking them in layers or maybe formed into single layers, respectively, and arranged in a matrix.Then, using the method shown in Embodiment 1, a silicon nitride film wasdeposited to 50 nm, thereby forming a protective film as a protectivelayer 9. Since the silicon nitride film has a high thermal conductivityand is formed sufficiently thin, it servers as the protective layer 9that also serves as a heat dissipating layer 11 even in this state.However, for carrying out heat dissipation more efficiently, Al wasdeposited by the sputtering method using a Xe plasma, which is shown inEmbodiment 1, thereby obtaining the heat dissipating layer 11.

As a result of measuring the luminance half-decay lifetime of thedisplay device thus obtained, the lifetime increased to 6000 hours whilebeing conventionally 2000 hours and, further, the light emitting areaincreased to an element area ratio of 80% while being conventionally 60%and thus the surface brightness increased by 20%. Since the organiclayers 10 were formed on the flattening film 41, there was no occurrenceof film formation failure or the like and thus the manufacturing yieldwas improved.

Embodiment 7

Referring to FIGS. 8A and 8B, a top emission type active matrix organicEL display device 44 according to Embodiment 7 includes a transparentsubstrate 2, a plurality of gate lines, a plurality of signal linesintersecting the gate lines, switching elements disposed atintersections of the gate lines and the signal lines, counter electrodes42 connected to the switching elements, an electron transport layer 7, alight emitting layer 6, and a hole transport layer 43 which form each oforganic layers 10 stacked on the counter pixel electrodes 42,respectively, conductive transparent pixel electrodes 3 formed on theorganic films of the organic layers 10 so as to be opposed to thecounter pixel electrodes 42, respectively, a protective layer 9 formedto directly or indirectly cover at least the organic layers 10, and aheat dissipating layer 11 formed to be in contact with the protectivelayer 9. In the organic layer 10, the electron transport layer 7, thelight emitting layer 6, and the hole transport layer 43 are formed fromthe side near the transparent pixel electrode 3.

The switching element is preferably a TFT element, an MIM element, orthe like that can control ON/OFF of the current. The TFT element ispreferable in terms of controllability of the brightness of the organicEL element.

Although it differs depending on a specification of a display device, aknown amorphous TFT or polysilicon TFT can be suitably used as the TFTelement.

Next, description will be mede as regards a method of manufacturing theactive matrix organic EL display device accoding to Embodiment 7. Atfirst, Al was formed into a 300 nm film by sputtering on a cleaned glasssubstrate. the sputtering, an Ar, Kr, or Xe gas can be suitably used.When Xe is used, since the electron collision sectional area is largeand the electron temperature is low, damage by a plasma to the formed Alfilm is suppressed, which is thus more preferable. Then, the formed Alfilm was patterned into gate lines and gate electrodes 24 by aphotolithography method. Then, using the dual shower plate microwaveplasma film forming apparatus used in Embodiment 1, silicon nitride wasformed into a 300 nm film at a substrate temperature of 200° C. and atAr:N₂:H₂:SiH₄=80:18:1.5:0.5, thereby obtaining a gate insulating film23. By setting the substrate temperature to 200° C., it was possible toform a high-quality silicon nitride film having a high withstand voltageand a small interface state density and thus capable of being used asthe gate insulating film 23. Then, using the same apparatus, amorphoussilicon was formed into a 50 nm film at a substrate temperature of 200°C. and at a volume ratio of Ar:SiH₄=95:5 and, subsequently, n+ amorphoussilicon was formed into a 30 nm film at Ar:SiH₄:PH₃=94:5:1. Bypatterning the stacked amorphous silicon and n+ silicon films by aphotolithography method, element regions were formed. Then, using thesame method as that shown in Embodiment 1, Al was formed into a filmusing a Xe plasma so as not to damage the elements and then waspatterned by a photolithography method, thereby obtaining signal lines,signal line electrodes 39, and conductive transparent pixel electrodes3. Then, using the patterned Al film as a mask, the n+ amorphous siliconlayer was etched by a known ion etching method, thereby forming TFTchannel separating regions. Using the dual shower plate microwave plasmafilm forming apparatus used in Embodiment 1, a silicon nitride film wasformed at room temperature, and then was subjected to patterning oforganic EL element regions by a photolithography method, therebyobtaining a protective film forming a protective layer 9 at each of theTFT channel separating portions and an insulating layer adapted toprevent a short between a conductive transparent electrode 3 and thecounter pixel electrode 42 of each organic EL element. Then, using themethod described in Embodiment 1, electron transport, light emitting,and hole transport layers 7, 6, and 43 were continuously formed and,without exposure to the atmosphere, an ITO containing 5 wt % Hf wasformed into a 150 nm film by the method described in Embodiment 1,thereby obtaining the conductive transparent electrodes 3. Then, siliconnitride was formed into a 50 nm film at room temperature by the dualshower plate microwave plasma film forming apparatus used in Embodiment1, thereby obtaining a protective layer 9. Since the protective layer 9has a high thermal conductivity of 80 W/(m·K) and is sufficiently thin,the thermal resistance is small and, therefore, it can also fully serveas a heat dissipating layer 11 alone. However, the heat dissipatinglayer 11 may also be provided separately for carrying out heatdissipation more efficiently. There is no particular limitation to amaterial of the transparent heat dissipating layer used in the topemission type as long as it has a high thermal conductivity and istransparent, and an ITO or the like is cited as an example.

According to the top emission type active matrix organic EL displaydevice thus obtained, since a buffer layer or a hole injection layerbecomes unnecessary because of a high work function possessed by theHf-containing ITO film, highly efficient light emission is enabled.Further, since use is made of the protective layer 9 having a highthermal conductivity and being thin, the protective layer 9 can suppresstemperature rise of the elements while fully achieving its function as aprotective layer, so that the element lifetime can be significantlyimproved. As a result of measuring the luminance half-decay lifetime ofthe display device shown in this Embodiment, it was improved to 9000hours while being conventionally 3000 hours.

Embodiment 8

Referring to FIGS. 9A and 9B, a transparent flattening film 41 may beformed on TFTs and, thereafter, organic EL elements may be formed. Withthis configuration, the organic EL elements can be formed on a flatsurface and, therefore, the manufacturing yield is improved. Further,since an organic EL layer is formed at a layer different from a signalline layer, pixel electrodes can be arranged so as to extend over thesignal wiring and thus it is possible to increase an area of each lightemitting element. Further, since signal lines can be formed of amaterial different from that of the pixel electrodes, it is notnecessary to use a conductive transparent material and, therefore, it ispossible to reduce a wiring resistance when a display device isincreased in size, thereby enabling an increase in display gradation. Atop emission type active matrix organic EL display device of Embodiment8 is formed in the following manner. At first, gate lines, TFT elements,and signal lines were formed by the method described in Embodiment 7.The signal lines were obtained by forming Al into a 300 nm film by thesputtering method using a Xe gas as shown in Embodiment 6 and patterningit by a photolithography method. Then, a photosensitive transparentresin was coated by a spin coating method, then was subjected toexposure and development, and then was dried at 150° C. for 30 minutes,thereby obtaining a flattening film 41. By the foregoing exposure anddevelopment processes, the flattening film was formed with connectingholes each for connection between a pixel-side electrode of the TFT andan organic EL element. As the photosensitive transparent resin, there isan acrylic resin, a polyolefin resin, an alicyclic olefin resin, or thelike. The alicyclic olefin resin is excellent in transparency with lessmoisture content and release and thus is preferable and, in thisEmbodiment, the alicyclic olefin resin was used. Then, using the methoddescribed in Embodiment 1, Al was formed into a film by the sputteringmethod using a Xe plasma and then was patterned by a photolithographymethod, thereby obtaining counter electrodes 42. Subsequently, electrontransport, light emitting, and hole transport layers 7, 6, and 43 werecontinuously formed by the method shown in Embodiment 1, and then, usingthe method likewise shown in Embodiment 1, an ITO film containing 5 wt %Hf was formed and then was patterned by a photolithography method,thereby obtaining conductive transparent pixel electrodes 3. In thelight emitting layer 6, materials adapted to emit light in red, green,and blue, respectively, may be used by optionally stacking them inlayers or may be formed into single layers, respectively, and arrangedin a matrix. Then, using the method shown in Embodiment 1, a siliconnitride film was deposited to 50 nm, thereby obtaining a protective filmforming a protective layer 9. Since the silicon nitride film has a highthermal conductivity and is formed sufficiently thin, it servers as theprotective layer 11 that also serves as a heat dissipating layer 11 evenin this state. However, the heat dissipating layer 11 may also beprovided separately for carrying out heat dissipation more efficiently.There is no particular limitation to a material of the transparent heatdissipating layer 11 used in the top emission type as long as it has ahigh thermal conductivity and is transparent, and an ITO or the like iscited as an example.

As a result of measuring the luminance half-decay lifetime of thedisplay device thus obtained, the lifetime increased to 9000 hours whilebeing conventionally 3000 hours and, further, the light emitting areaincreased to an element area ratio of 80% while being conventionally 60%and thus the surface brightness increased by 20%. Since the organiclayers 10 were formed on the flattening film 41, there was no occurrenceof film formation failure or the like and thus the manufacturing yieldwas improved.

Embodiment 9

Referring to FIGS. 10A and 10B, a bottom emission type active matrixorganic EL display device 46 according to Embodiment 9 includes atransparent substrate 2, a plurality of gate lines, a plurality ofsignal lines intersecting the gate lines, switching elements disposed atintersections of the gate lines and the signal lines, conductivetransparent pixel electrodes 36 connected to the switching elements, ahole transport layer 5, a light emitting layer 6, and an electrontransport layer 5 which form each of organic layers 10 stacked on thetransparent pixel electrodes 36, respectively, counter electrodes 8formed on the organic films of the organic layers 10 so as to be opposedto the conductive transparent pixel electrodes 36, respectively, aprotective layer 9 formed to directly or indirectly cover at least theorganic layers 10, and a heat dissipating layer 11 formed to be incontact with the protective layer 9. In the organic layer 10, the holetransport layer 5, the light emitting layer 6, and the electrontransport layer 7 are formed from the side near the transparent pixelelectrode 36.

The switching element is preferably a TFT element, an MIM element, orthe like that can control ON/OFF of the current. The TFT element ispreferable in terms of controllability of the brightness of the organicEL element.

Although it differs depending on a specification of a display device, aknown amorphous TFT or polysilicon TFT can be suitably used as the TFTelement.

Next, description will be made as regards a method of manufacturing theactive matrix organic EL display device 46 iaccording to Embodiment 9.At first, using the dual shower plate microwave-excited plasma filmforming apparatus used in Embodiment 1, polysilicon was formed into a 50nm film on a cleaned glass substrate at a substrate temperature of 200°C. and at a volume ratio of Ar:SiH₄=95:5 while applying a high frequencyof 13.56 MHz from the substrate and performing ion irradiation and thenwas patterned by a photolithography method, thereby obtaining TFTelement regions. Then, using the same apparatus, silicon nitride wasformed into a 300 nm film at a substrate temperature of 200° C. and atAr:N₂:H₂:SiH₄=80:18:1.5:0.5, thereby obtaining a gate insulating film33. By setting the substrate temperature to 200° C., it was possible toform a high-quality silicon nitride film having a high withstand voltageand a small interface state density and thus capable of being used asthe gate insulating film 33. Subsequently, Al was formed into a 300 nmfilm by sputtering. In the sputtering, an Ar, Kr, or Xe gas can besuitably used. When Xe is used, since the electron collision sectionalarea is large and the electron temperature is low, damage by a plasma tothe formed Al film is suppressed, which is thus more preferable. Then,the formed Al film was patterned into gate lines and gate electrodes bya photolithography method. Then, using the dual shower plate microwaveplasma film forming apparatus used in Embodiment 1, silicon nitride wasformed into a 300 nm film at a substrate temperature of 200° C. and atAr:N₂:H₂:SiH₄=80:18:1.5:0.5. The formed silicon nitride film was formedwith contact holes by a photolithography method. Then, using the samemethod as that shown in Embodiment 1, an ITO containing 5 wt % Hf wasformed into a 350 nm film and then was patterned by a photolithographymethod, thereby obtaining signal lines, signal line electrodes 29, andconductive transparent pixel electrodes 36. Then, using the methoddescribed in Embodiment 1, hole transport, light emitting, and electrontransport layers 5, 6, and 7 were continuously formed as organic layers10 and, without exposure to the atmosphere, Al was formed into a filmusing a Xe plasma with a low electron temperature by the use of the Alsputtering apparatus used for the formation of the gate lines, therebyobtaining counter electrodes 8. Then, silicon nitride was formed into a50 nm film at room temperature by the dual shower plate microwave plasmafilm forming apparatus used in Embodiment 1, thereby obtaining aprotective layer 9. Since the protective layer 9 has a high thermalconductivity of 80 W/(m·K) and is sufficiently thin, the thermalresistance is small and, therefore, it can also fully serve as a heatdissipating layer alone. However, a heat dissipating layer 11 may alsobe provided separately for carrying out heat dissipation moreefficiently. In this Embodiment, Al was formed into a film using a Xeplasma with a low electron temperature by the use of the Al sputteringapparatus used for the formation of the gate lines, thereby obtainingthe heat dissipating layer 11.

According to the bottom emission type active matrix organic EL displaydevice thus obtained, since a buffer layer or a hole injection layerbecomes unnecessary because of a high work function possessed by theHf-containing ITO film, highly efficient light emission is enabled.Further, since polysilicon is used as the TFT elements, the currentdrive performance is improved and thus the controllability of theorganic EL elements is excellent, thereby enabling high-quality display.Further, since use is made of the protective layer 9 having a highthermal conductivity and being thin, the protective layer 9 can suppresstemperature rise of the elements while fully achieving its function as aprotective layer, so that the element lifetime can be significantlyimproved. As a result of measuring the luminance half-decay lifetime ofthe display device shown in this Embodiment, it was improved to 6000hours while being conventionally 2000 hours.

Embodiment 10

As shown in FIGS. 11A and 11B, a flattening film 41 may be formed onTFTs and, thereafter, organic EL elements may be formed. With thisconfiguration, the organic EL elements can be formed on a flat surfaceand, therefore, the manufacturing yield is improved. Further, since anorganic EL layer is formed at a layer different from a signal linelayer, pixel electrodes 36 can be arranged so as to extend over thesignal wiring and thus it is possible to increase an area of each lightemitting element. Further, since signal lines can be formed of amaterial different from that of the pixel electrodes 36, it is notnecessary to use a conductive transparent material and, therefore, it ispossible to reduce a wiring resistance when a display device isincreased in size, thereby enabling an increase in display gradation.

A bottom emission type active matrix organic EL display device 48 ofEmbodiment 10 is formed in the following manner. At first, TFT elements,gate lines, and signal lines were formed by the method described inEmbodiment 9. The signal lines were obtained by forming Al into a 300 nmfilm by the sputtering method using a Xe gas as shown in Embodiment 6and patterning it by a photolithography method. Then, a photosensitivetransparent resin was coated by a spin coating method, then wassubjected to exposure and development, and then was dried at 150° C. for30 minutes, thereby obtaining a flattening film 41. By the foregoingexposure and development processes, the flattening film was formed withconnecting holes each for connection between a pixel-side electrode ofthe TFT and an organic EL element. As the photosensitive transparentresin, there is an acrylic resin, a polyolefin resin, an alicyclicolefin resin, or the like. The alicyclic olefin resin is excellent intransparency with less moisture content and release and thus ispreferable and, in this Embodiment, the alicyclic olefin resin was used.

Then, using the method described in Embodiment 1, an ITO film containing5 wt % Hf was formed and then was patterned by a photolithographymethod, thereby obtaining conductive transparent pixel electrodes 36.Subsequently, hole transport, light emitting, and electron transportlayers 5, 6, and 7 were continuously formed by the method shown inEmbodiment 1, and then Al was formed into a film by the sputteringmethod using a Xe plasma, which is likewise shown in Embodiment 1,thereby obtaining counter electrodes 8. In the light emitting layer 6,materials adapted to emit light in red, green, and blue, respectively,may be used by optionally stacking them in layers or may be formed intosingle layers, respectively, and arranged in a matrix. Then, using themethod shown in Embodiment 1, a silicon nitride film was deposited to 50nm, thereby forming a protective film. Since the silicon nitride filmhas a high thermal conductivity and is formed sufficiently thin, itservers as the protective layer 9 that also serves as a heat dissipatinglayer 11 even in this state. However, for carrying out heat dissipationmore efficiently, Al was deposited by the sputtering method using a Xeplasma, which is shown in Embodiment 1, thereby obtaining the heatdissipating layer 11.

As a result of measuring the luminance half-decay lifetime of thedisplay device thus obtained, the lifetime increased to 6000 hours whilebeing conventionally 2000 hours and, further, the light emitting areaincreased to an element area ratio of 80% while being conventionally 60%and thus the surface brightness increased by 20%. Since the organiclayers 10 were formed on the flattening film 41, there was no occurrenceof film formation failure or the like and thus the manufacturing yieldwas improved. Further, since polysilicon is used as the TFT elements,the current drive performance is improved and thus the controllabilityof the organic EL elements is excellent, thereby enabling high-qualitydisplay.

Embodiment 11

In the bottom emission type active matrix display device shown inEmbodiment 9, by changing the formation order between the counterelectrode 42 and the conductive transparent electrode 3 and theformation order between the electron transport layer 7 and the holetransport layer according to the same method as that shown in Embodiment7, it is possible to obtain a top emission type active matrix displaydevice 50.

Referring to FIGS. 12A and 12B, in the top emission type active matrixdisplay device thus formed, although a substrate 29 is not limited aslong as its surface is insulative, use was made of a metal substrateformed with a silicon nitride film on the surface thereof. As TFTelements, use was made of polysilicon TFTs shown in Embodiment 10.

According to the bottom emission type active matrix organic EL displaydevice 50 thus obtained, since a buffer layer or a hole injection layerbecomes unnecessary because of a high work function possessed by theHf-containing ITO film, highly efficient light emission is enabled.Further, since polysilicon is used as the TFT elements, the currentdrive performance is improved and thus the controllability of theorganic EL elements is excellent, thereby enabling high-quality display.Further, since use is made of the protective layer 9 having a highthermal conductivity and being thin, the protective layer 9 can suppresstemperature rise of the elements while fully achieving its function as aprotective layer, so that the element lifetime can be significantlyimproved. As a result of measuring the luminance half-decay lifetime ofthe display device shown in this Embodiment, it was improved to 9000hours while being conventionally 3000 hours.

Embodiment 12

In the bottom emission type active matrix display device shown inEmbodiment 10, by changing the formation order between the counterelectrode and the conductive transparent electrode and the formationorder between the electron transport layer and the hole transport layeraccording to the same method as that shown in Embodiment 8, it ispossible to obtain a top emission type active matrix display device.

Referring to FIGS. 13A and 13B, in the top emission type active matrixdisplay device thus formed, although a substrate 29 is not limited aslong as its surface is insulative, use was made of a metal substrateformed with a silicon nitride film on the surface thereof. As TFTelements, use was made of polysilicon TFTs shown in Embodiment 11.

According to the bottom emission type active matrix organic EL displaydevice 51 thus obtained, since a buffer layer or a hole injection layerbecomes unnecessary because of a high work function possessed by theHf-containing ITO film, highly efficient light emission is enabled.Further, since polysilicon is used as the TFT elements, the currentdrive performance is improved and thus the controllability of theorganic EL elements is excellent, thereby enabling high-quality display.Further, since use is made of the protective layer 9 having a highthermal conductivity and being thin, the protective layer 9 can suppresstemperature rise of the elements while fully achieving its function as aprotective layer, so that the element lifetime can be significantlyimproved. As a result of measuring the luminance half-decay lifetime ofthe display device shown in this Embodiment, it was improved to 9000hours while being conventionally 3000 hours. Further, the light emittingarea increased to an element area ratio of 80% while beingconventionally 60% and thus the surface brightness increased by 20%.Further, since the organic layers 10 were formed on the flattening film41, there was no occurrence of film formation failure or the like andthus the manufacturing yield was improved.

Embodiment 13

Referring to FIGS. 14 and 14B, a bottom emission type organic EL displaydevice 52 accoding to Embodiment 13 includes a transparent substrate 2,a plurality of gate lines, a plurality of signal lines intersecting thegate lines, switching elements disposed at intersections of the gatelines and the signal lines, conductive transparent pixel electrodes 36connected to the switching elements, a hole transport layer 5, a lightemitting layer 6, and an electron transport layer 7 which form each oforganic layers 10 stacked on the transparent pixel electrodes 36,respectively, counter electrodes 8 formed on the organic films of theorganic layers 10 so as to be opposed to the transparent pixelelectrodes 36, respectively, a protective layer 9 formed to directly orindirectly cover at least the organic layers 10, and a heat dissipatinglayer 11 formed to be in contact with the protective layer 9. In theorganic layer 10, the hole transport layer 5, the light emitting layer6, and the electron transport layer 7 are formed from the side near thetransparent pixel electrode 36.

The TFT elements and the display device of this Embodiment are formed inthe following manner. At first, a photosensitive transparent resin iscoated to 350 nm on a cleaned substrate and then is exposed anddeveloped, thereby forming openings in gate line and gate electroderegions. Then, a metal film is formed in the openings to a thicknessequal to that of the photosensitive transparent resin by a screenprinting method, an injection printing method, a plating method, or thelike, thereby obtaining gate lines and gate electrodes 34. While amaterial of the metal film can be properly selected depending on amanufacturing method, Au, Cu, Ag, Al or the like having a lowresistivity is preferable. In this Embodiment, Ag was selected as awiring material. Then, using the dual shower plate microwave plasma filmforming apparatus used in Embodiment 1, silicon nitride was formed intoa 300 nm film at a substrate temperature of 200° C. and atAr:N₂:H₂:SiH₄=80:18:1.5:0.5, thereby obtaining a gate insulating film33. By setting the substrate temperature to 200° C., it was possible toform a high-quality silicon nitride film having a high withstand voltageand a small interface state density and thus capable of being used as agate insulating film. Then, using the same apparatus, amorphous siliconwas formed into a 50 nm film at a substrate temperature of 200° C. andat a volume ratio of Ar:SiH₄=95:5 and, subsequently, n+ amorphoussilicon was formed into a 30 nm film at Ar:SiH₄:PH₃=94:5:1. Bypatterning the stacked amorphous silicon and n+ silicon films by aphotolithography method, element regions were formed. Then, using thesame method as that shown in Embodiment 1, an ITO containing 5 wt % Hfwas formed into a 350 nm film and then was patterned by aphotolithography method, thereby obtaining signal lines, signal lineelectrodes 29, and conductive transparent pixel electrodes 36. Then,using the patterned ITO film as a mask, the n+ amorphous silicon layerwas etched by a known ion etching method, thereby forming TFT channelseparating regions. Using the dual shower plate microwave plasma filmforming apparatus used in Embodiment 1, a silicon nitride film wasformed at room temperature, and then was subjected to patterning oforganic EL element regions by a photolithography method, therebyobtaining a protective film forming a protective layer 9 at each of theTFT channel separating portions and an insulating layer adapted toprevent a short between the conductive transparent electrode 36 and acounter electrode 8 of each organic EL element. Then, using the methoddescribed in Embodiment 1, hole transport, light emitting, and electrontransport layers 5, 6, and 7 were continuously formed as organic layers10 and, without exposure to the atmosphere, Al was formed into a filmusing a Xe plasma with a low electron temperature by the use of an Alsputtering apparatus used for the formation of the gate lines, therebyobtaining the counter electrodes 8. Then, silicon nitride was formedinto a 50 nm film at room temperature by the dual shower plate microwaveplasma film forming apparatus used in Embodiment 1, thereby obtaining aprotective layer 9. Since the protective layer 9 has a high thermalconductivity of 80 W/(m·K) and is sufficiently thin, the thermalresistance is small and, therefore, it can also fully serve as a heatdissipating layer 11 alone. However, the heat dissipating layer 11 mayalso be provided separately for carrying out heat dissipation moreefficiently. In this embodiment, Al was formed into a film using a Xeplasma with a low electron temperature by the use of the Al sputteringapparatus used for the formation of the gate lines, thereby obtainingthe heat dissipating layer 11.

According to the bottom emission type active matrix organic EL displaydevice thus obtained, since a buffer layer or a hole injection layerbecomes unnecessary because of a high work function possessed by theHf-containing ITO film, highly efficient light emission is enabled.Further, since use is made of the protective layer 9 having a highthermal conductivity and being thin, the protective layer 9 can suppresstemperature rise of the elements while fully achieving its function as aprotective layer, so that the element lifetime can be significantlyimproved. As a result of measuring the luminance half-decay lifetime ofthe display device shown in this Embodiment, it was improved to 6000hours while being conventionally 2000 hours. Further, since it isconfigured such that the gate electrodes are embedded, the semiconductorlayers forming the TFTs can be formed on a flat surface and thus it ispossible to suppress current variation of the TFTs. Therefore, not onlythe display quality is improved, but also lifetime variation of theorganic EL elements due to current variation can be suppressed.

A polysilicon layer may be used instead of the amorphous silicon layersaccording to the method shown in Embodiment 9. In this case, since thecurrent drive performance of the TFTs is improved, the controllabilityof light emission of the organic EL elements is improved, therebyenabling an improvement in display quality.

Further, as shown in Embodiments 7 and 11, the top emission typestructure may be employed by switching between the counter electrode 8and the conductive transparent electrode 36 and between the electrontransport layer 7 and the hole transport layer 5, respectively. In thiscase, it is possible to improve the efficiency of light extraction fromthe organic EL elements.

Further, as shown in Embodiments 6, 8, 10, and 12, it may be configuredsuch that the flattening film 41 is formed on the TFTs and the organicEL elements are formed thereon. In this case, since the organic ELlayers are formed on the flat surface, film formation failure or thelike is suppressed. Therefore, the element lifetime is improved and,further, it becomes possible to suppress variation in brightness andvariation in lifetime.

Embodiment 14

Referring to FIG. 15, a heat dissipating layer 11 according toEmbodiment 14 exemplifies the heat dissipating layer 11 of the displayelement in Embodiment 1. The heat dissipating layer 11 of thisEmbodiment has a comb-shaped pattern on its surface, thereby increasingan area contacting an external layer, for example, an air layer, toachieve an improvement in heat dissipation efficiency. With theconfiguration of this comb-shaped electrode, the heat dissipationefficiency was improved, so that the luminance half-decay lifetime ofthe element was improved by 20%. Although the comb-shaped structure isemployed in this Embodiment, lands and recesses on an emboss or the likemay be employed as long as it is a structure that can increase thecontact area with an external layer. Further, the heat dissipating layer11, when not serving as a protective layer 9, does not need to cover theentire surface of the element, but may cover at least a light emittingregion. It may be configured such that adjacent heat dissipating layersare connected together and another heat dissipation means such as aheatsink or a Peltier element is provided outside the element.

Further, in the case of the top emission type, there may be providedlands and recesses of about several nm to several ten nm sufficientlyshorter than a wavelength of light or there may be provided a matrixlattice shape with a height of several microns so as to match a shape ofa black matrix. This can improve the heat dissipation effect by aboutseveral %.

As described above, according to the Embodiments of this invention,since the work function of ITO can be increased to about 5.5 eV by theHf-containing ITO film, the hole injection efficiency in the organic ELelement is improved to thereby make unnecessary a hole injection layeror a buffer layer that is generally required and, therefore, the lightemitting efficiency is improved, thereby enabling an improvement inbrightness. Further, the calorific value is reduced by a reduction inenergy barrier to the light emitting layer, so that the lifetime of theorganic EL element can be improved.

Further, according to this invention, since a nitride is used as aprotective layer of an organic EL light emitting layer, it is possibleto obtain a stable protective layer with a high thermal conductivity andwith no permeation of moisture or an oxidizing gas even in the form of athin film. Since the heat generated in the light emitting layer can beefficiently released to the outside, the lifetime of an organic ELelement can be improved. According to a display element of thisinvention, since a nitride protective film is formed by low-temperaturevapor deposition, it is possible to prevent damage to an organic ELlayer. Further, according to a display element of this invention, sincean organic EL element can be formed on a flat structure, film formationfailure or the like is reduced, so that the lifetime of the element canbe improved. Further, according to a display element of this invention,since an organic EL electrode and a signal line can be arranged atdifferent wiring layers, a display area can be increased to therebyenable an improvement in screen brightness. Further, according to adisplay element of this invention, since an organic EL electrode and asignal line can be arranged at different wiring layers, the signal lineand the electrode of the organic EL element can include differentmaterials and, therefore, an electrical resistance of the signal linecan be reduced, so that a large-size display device can be configured.Further, according to a display device of this invention, since embeddedgate structure TFTs can be used, semiconductor regions of the TFTelements can be configured to be substantially flat, thereby enabling areduction in current variation of the TFT elements. Accordingly, it ispossible to suppress variation in lifetime of organic EL elements whilerealizing high-quality display.

INDUSTRIAL APPLICABILITY

As described above, an organic EL light emitting element according tothis invention is most suitable for a liquid crystal display device, amonitor of a television, or the like.

1-39. (canceled)
 40. A display device comprising a plurality of organiclight emitting element, each organic light emitting element including aconductive transparent electrode, a counter electrode opposed to saidconductive transparent electrode, a light emitting layer providedbetween said conductive transparent electrode and said counterelectrode, and a heat dissipating layer contacting and provided to coverthe organic light emitting element, wherein the heat dissipating layerlands and recesses on the surface of the heat dissipating layer.
 41. Adisplay device according to claim 40, wherein a comb-shaped pattern isformed on the surface of the heat dissipating layer.
 42. A displaydevice according to claim 40, wherein said heat dissipating layer isprovided only in a light emitting region of said plurality of organiclight emitting element.
 43. A display device comprising a plurality oforganic light emitting element, each organic light emitting elementincluding a conductive transparent electrode, a counter electrodeopposed to said conductive transparent electrode, a light emitting layerprovided between said conductive transparent electrode and said counterelectrode, a protective layer contacting the organic light emittingelement, and a heat dissipating layer contacting the protective layerand provided to cover the organic light emitting element, wherein theheat dissipating layer lands and recesses on the surface of the heatdissipating layer.
 44. A display device according to claim 43, theprotective layer comprising a nitride of an element selected from thegroup consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, B, Al and Si.
 45. Adisplay device according to claim 43, wherein a thickness of theprotective layer is 10 nm or more and 100 nm or less.
 46. A displaydevice according to claim 43, wherein a comb-shaped pattern is formed onthe surface of the heat dissipating layer.
 47. A display deviceaccording to claim 43, wherein the heat dissipating layer is providedonly in a light emitting region of said plurality of organic lightemitting element.